Blast noise suppressor for an explosive operated kiln device



Feb. 23, 1960 c, R s

BLAST NOISE SUPPRESSOR FOR AN EXPLOSIVE OPERATED KILN DEVICE Filed Aprll 1 1957 LIX...

INVENTOR. ALVA C. KR U5 KM (2W ATTORNEYf:

BLAST NOISE SUPPRESSOR FOR AN EXPLOSIVE OPERATED KILN DEVICE This invention relates to kilns for the manufacture of cement or the like finished materials formed by fusing of raw materials in rotating heated apparatus and in particular relates to a kiln gun device for explosively removing clinker rings from rotary kilns.

Heretofore, one of the most effective ways of removing the clinker ring which gradually builds up inside the kiln involves the use of a kiln tool sometimes referred to as a kiln gun. By means of such kiln devices the operator of the kiln can remove the ring by aiming and shooting a number of lead alloy slugs designed to resist fragmentation and produce a smashing sledge-hammer like blow upon any desired portion of the ring. Being flat-ended, and fairly heavy, these slugs driven at high energy level can smash a keyway or two through the clinker ring instead of penetrating it after which the ring falls and crumbles and the kiln is again ready for operation with a minimum of delay. Although the removal of a ring by such devices is rapid and convenient as well as economical, it has involved in certain instances a disagreeable and sometimes uncomfortably loud noise.

The source of noise includes not only the crack of the high compression spherical pulses and their wave envelope coming from the slug projected at super-sonic velocities but also the low frequency high-intensity blast or boom from the muzzle of the slug projector or gun, which blast includes various other sounds and reverberations. From these sources the noise generated is of the non-periodic type having a very complex wave form and is borne with considerable intensity of both positive and negative peak pressures to the observer at the kiln. Inasmuch as the kiln has broad walls and is relatively open at the discharge end through a port hole of which the slugs are projected, any excessive noise generated is borne directly with little or no diminution or is reverberated and then radiated laterally and especially rearwardly from the shield and its port hole at great loudness.

Various muffiing devices have been tried but have proved either ineffective or unserviceable for one reason or another such as their excessive weight or the tendency for such devices to pick-up and become clogged with lead from the slug.

One object of the present invention is to provide a novel and eifective means for dissipating the impact of noise which frequently is excessive and always accompanics the use of explosively actuated clinker ring removing devices. A further object of the invention is to provide compact and relatively light-weight means of improved design for abatement of the noise readily adapted for mounting upon the end of a burning kiln. To accomplish these and other objects which will be apparent hereinafter the invention consists in the novel combination and arrangement of parts specifically ineluding an explosive slug projector, an enclosure with bafiies and compartments of desired size, spacing and volume suitable for functioning effectively under the 2,925,755 Patenteel Feh 23, 1960 tion of the noise abating parts in accordance with this invention.

The invention for illustrative purposes is described in connection with a slug projector generally of the type disclosed in the co-pending application of H. C. Foster, Serial No. 400,431 filed December 28, 1953, now Patent as to provide means such as hub 8 receiving an outer In the typical arrangement shown in Figure 1, the gun I is mounted in any suitable manner such as by being fastened to an I-beam 2 mounted in turn on a heat shield 3, which consists of a thick wall of refractory material such as fire brick laid up on a steel frame which in turn is mounted, sometimes on wheels, so as to be adjacent and sometimes movable toward or away from the otherwise open discharge end of the kiln 4. The refractory Wall or shield 3 is provided with a suitable opening or porthole 5 into which the muzzle 6 of the gun is mounted in position for projecting the slugs into any desired section of the clinker ring.

A portion of the tool gun structure such as the frame 7 adjacent the muzzle is constructed in such a manner muffler tube or casing 10. The mounting hub 8 issuch that together with the rear end of the casing it forms a substantial closure rearwardly of the muzzle 6, except for a small clearance space as shown in Figures 2 and 3 at which barrel 6 and hub 8 are preferably mounted in slidable relationship with respect to each other to provide for recoil displacement.

As shown in Figures 2 and 3, mounted within the casing 10 is a series of relatively thin baflies 11, 12 and 13 of ring shape each defining a central aperture. These rings are arranged in longitudinally spaced relationship with respect to each other and with respect to the casing mounting means or rear end closure 8 in such a way as to define casing compartments 20, 21 and 22. Compartment 20. is a cylindrical compartment surrounding and including the muzzle 6. Compartments 21 and 22 are smaller compartments compared to compartment 20 and are of annular shape. At the forward end of casing 10 there is provided a mufiier extension 50 which alsoserves to shield the endmost bafiie ring 13. The entire assembly of bafllerings and the'casingis detachably mounted to the frame 7 at the end closing, hub 8 by means of a suitable number of fasteners suchas the cap screws 51. This type of mounting facilitates separation of the explosive operated clinker removing device in the event expendable'parts such as the barrel must be replaced.

The arrangement of this invention is particularly adapted for association with kiln ring removing tools' I 3 to 3 /2 ounces and inasmuch as the powder charge is afairly high one suitable for driving the slug at the relatively high-muzzleenergy of around 7500 foot pounds and even higher. Correspondingly, the explosive blast which accompanies each shot is at a substantially higher H level of -intensity than themuzzle blast or boom which accompanies an ordinary shotgun firing. Furthermore, under the circumstances of use reflection and reverberation frequently intensify the, noise detected by the gun loader or operator or any observer for that matter.

It has been found that'the rather simple lightweight construction of this invention has been remarkably effective in abating the noise to a relatively comfortable level.

The tubular heat resistant casing 10, according to a preferred specific embodiment, consists of a piece of standard cold rolled seamless steel tubing having an inside diameter of about 4 /2 inches and an outside diameter of about 4% inches and a length of about 26 to 28 inches. At the rear end, the casing is supported on the mounting hub 8 which extends from the gun mounting frame 7 by about three inches into the rear end of casing 10 to form substantial closure about the kiln tool barrel which also extends through hub 8 into the interior of the casing. Mounted within the interior of the imperforate casing about 12 inches from the front end is a first bafile ring 11 fastened in any suitable manner such as by being welded to a rather thick base ring 14 which in turn is fastened to the casing 10 by any suitable means such as a series of rivets 15. Also mounted in the casing about inches ahead of ring 11 is a second ring 12 supported on a base ring 16 and fastened by rivets 17 to the casing 10. Similarly a third ring 13, base ring 18 and rivets 19 are arranged to place the ring 13 about 5 inches ahead of the second or intermediate ring 12. This arrangement leaves an extension 50 of about 2 inches at the front end of the casing which prevents deformation of the relatively thin end ring 13 during the handling of the unit. The rings 11, 12 and 13 are formed preferably of stainless steel and are seamless.

The structure of the base rings 14, 16 and 18 is heavy compared to the thin baffle rings 11, 12 and 13 and forms a strong base or root structure for each baffle ring providing the advantage of secure attachment to the casing 10. The muzzle facing edge of at least the first base ring 14 is wedge-shaped for improving the airflow and thereby not only enhancing the attenuation but also avoiding lead accumulation. The construction as shown has been found to have considerable resistance to fracture.

In this preferred embodiment each of the rings 11, 12 and 13 is of a frusto-conical shape the smaller ends of which form the central apertures 31, 32 and 33, respectively, each of a diameter of about 2 inches in alignment with the muzzle 6 of the tool. The conical shape of each ring preferably makes an angle of about 45 with the longitudinal or axial direction of the tool barrel and casing and is disposed in such a way as to converge forwardly or in the upstream direction at each of the central apertures 31, 32 and 33. As a still further preferred arrangement in this embodiment each of rings 11, 12 and 13 is provided with a series of about eight relatively large holes of a diameter of about of an inch. The oblique angle of approximately 45 and the upstream convergence are advantageous.

This particular arrangement provides a first blast attenuation cylindrical compartment 20 having a length of about 11 to 13 inches and a diameter of about 4 /2 inches into which the muzzle 6 of the barrel extends to occupy a volume about 2 inches in diameter and about 7 inches or less in length. This relatively long large first compartment is open at orifice 3'1 but is elfectively closed at the rear end by means of the hub 8 and forms a first expansion reservoir for slowing down the rapidly expanding gases ejected at the muzzle. In association with this compartment are the annular chambers 21 and 22 each of which are slanted and constitute a sound wave attenuating compartment having an outer diameter of about 4 /2 inches and having an annular opening or necks of adiameter-of about Z-inchesand a gap width of about 5 inches. These openings or neck are defined and separated by the relatively thin walls of the slanted rings having a thickness of about of an inch.

The preferred frusto-conical configuration of the rings 11, 12 and 13, aperture-size, ring spacing and the provision of an array of smaller perforations surrounding each of the central apertures therein have definite advantage for this particular purpose. The forwardly converging arrangement reduces the shock on the baffle rings while having an attenuating effect which is the reverse of a megaphone effect. Moreover, the shape tends to provide some degree of turbulence and eddying to the expanding gases and minimizes the occurrence of spaces wherein particles from the slug-can accumulate. As the gases pass through the central apertures 31, 32 and 33 they undergo alternate contraction and expansion; and a further turbulent effect is provided as some of the gas is drawn through the smaller perforations 41, 42 and 43 by the aspirating effect of the central flow of gases through the apertures 31, 32 and 33. The sound waves are trapped to a considerable extent in the annular compartments 21 and 22 which have a high absorption capacity for the range of sound wave frequencies involved, in view of the large gap width, thinness of the partitions and other dimensional volumetric relationships. The arrangement thus sets up multiple-wave reflections, turbulence and mechanical filtering so as to break up the sound waves thereby changing the coupling and suppressing the noise and shock pressure following the projectile.

As an illustrative example, in one particular industrial typical installation of the device of this invention a considerable reduction in noise was obtained. Measurements of the noise level were taken with an Altee- Lansing ZIBR 180 high-intensity microphone and a dualchannel Magnecord tape recorder modified with special peak indicators to prevent overloading the tape. A transistor oscillator was used for calibration of the tape. With the aid of this equipment measurements were taken for a tool having no mufiler and a tool having another type of mufiler as well as a tool in accordance with this invention. Measurements were taken using both regular and heavy explosive charge and slug loads. For each condition noise measurements were made at two locations A and B near the gun in a vicinity near the loader and operator, respectively, at a position C 10 feet to one side of the gun, and at another position D 10 feet directly to the rear of the tool. The results obtained for positive peak, negative peak and average sound pressure levels are given in the following tables in terms of decibels.

Table I.Positive peak Test Place A B O D No Mufiie 156 155 148 148 No Muflie, hi-loaCL 158 158 158 150 Mufiie A 159 160 149 152 Mufile B. 144 151 141 145 Mufiie B. 152 154 147 147 This device a 140 143 136 This device, hi-load 140 149 141 141 Table Il.-Negative peak Test Place A B C D 154 156 151 147 156 158 150 148 149 150 141 140 ufiie B 146 151 141 Mulfie B, hl-load 151 152 141 145 This device 142 145 138 138 This device, hi-load 141 146 137 140 Table III.--Average sound pressure The results shown in the table indicate that the device of this invention produced a considerable abatement of noise both on regular and on heavy loads. At position A the reduction in peak pressure was about decibels, at position B the reduction was about 11 decibels. At the other positions the average reduction of the peak sound pressure level was about 7 decibels. The average sound pressure levels on the basis of a 2 millisecond averaging time are all reduced about 10 decibels. These results mean that relative to the original noise levels, the noise has been reduced about 50% or more and that a considerable number of rounds can be fired with the tool of this invention without excessive noise and in relative comfort.

The device shown and described as a kiln tool is intended to be illustrative of the large caliber explosive actuated tool of this invention suitable'for projecting an impact member into kilns, furnaces, structure members and the like rather than being limited to a kiln device, and it is to be understood that various changes and modifications in construction may be made and may occur to those skilled in the art without departing from the spirit and scope of the invention asset forth in the appended claims.

What is claimed is:

1. An explosive actuated tool having a barrel for projecting an impact member against a workpiece in close juxtaposition with the muzzle of said barrel, said barrel and impact member having a caliber equivalent to the caliber of a shotgun within the range of from about 4 gauge to about 8 gauge, and including a blast noise suppressor comprising a tubular casing of imperforate side wall construction having a transverse dimension of about 4 /2 inches and said casing being open at the front end for passage of said impact member and being substantially closed at the rear end about a lesser opening, the muzzle end of said barrel being operatively received in said lesser opening and supporting said suppressor, a plurality of baflie rings, mounted in said casing in a longitudinal spaced relationship, each of said rings having a central aperture in alignment with said casing openings, the muzzle of said barrel and the other ring apertures, said rings having front and rear faces of frusto-conical shape each converging from its muzzle-facing end forwardly to its aperture to form along said casing length in front of said barrel muzzle about two gas expansion and sound wave attenuating compartments in front of said barrel muzzle wherein the hot gases of the tool muzzle blast are permitted to expand rapidly and become dissipated without the excessive accumulation of particles from said impact memher, said rings being longitudinally relatively thin as compared to said compartments, adjacent rings having said front'and rear faces spaced in said casing with respect to each other by about five inches to form said compartments, one of said rings being spaced from said rear end of the casing to form a rear compartment of larger volume compared to said other compartments, said larger compartment containing said barrel muzzle, said casing being of a length suflicient to accommodate all said compartments, said length being substantially not in excess of about from 26 to 28 inches.

2. The tool of claim 1 wherein the rings have a plurality of perforations about the central aperture and having a relatively thick circumferential root section fastened to the tubular casing, said root section having a frusto-conical edge facing the rear end of the casing and converging forwardly.

3. The tool of claim 1 wherein the frusto-conical rings consist of a tough heat resistant metal and have about a 45 shape with a plurality of perforations about the central aperture.

4. .A tool for removing an encrustation such as a kiln clinker ring from a kiln, furnace or the like by. projection of a slug against said incrustation comprisingan explosive actuated impact slug projecting mechanism including a barrel having a muzzle held in juxtaposition with respect to an access opening of said kiln and. a caliber equivalent to at least about an 8 gauge shotgun and a blast noise suppressor applied to the muzzle thereof comprising a tubular casing of'substantially cylindrical imperforate sidewall constructionhaving a front end opening for passage of said impact slug and a length of about 26 to 28 inches and an internal diameter of about 4% inches enclosing a first attenuating barrel muzzle receiving compartment of a length of about 11 to 13 inches and also second and third compartments ahead of said first compartment and communicating with each other and said first compartment through bafile rings of stainless steel having aligned central apertures of a diameter of about 2 inches in line with said front end opening and barrel and a plurality of perforations of a diameter of about of an inch arrayed uniformly about said apertures, said rings being spaced from each other by about 5 inches, having a thickness of about A of an inch and being of frusto-conical shape converging forwardly at an angle of about 45 with said casing which is substantially closed at its rear end about said barrel passing through an opening in said rear end in slidable relationship.

5. The tool of claim 4 wherein the rings have a relatively thick circumferential root section, said root section having a frusto-conical edge facing the rear end of the casing and converging forwardly.

References Cited in the file of this patent UNITED STATES PATENTS LOomis Feb. '18, 1947 

